1. Field of the Invention
This invention relates to computer systems and, more particularly, to backup and restoration of data within computer systems.
2. Description of the Related Art
There is an increasing need for organizations to protect data that resides on a variety of client devices via some type of backup mechanism. For example, numerous client devices may be coupled to a network to which one or more backup servers are also coupled. The backup servers may include or be further coupled to one or more disk storage devices, tape drives, or other backup media. A backup agent on each client device may convey data files to the backup server for storage on backup media according to a variety of schedules, policies, etc. For example, large backup datasets may be moved from a client device to a media server configured to store data for later retrieval, thereby protecting data from loss due to user error, system failure, outages, and disasters, etc. as well as archiving information for regulatory compliance, workflow tracking, etc.
In order to minimize the size of storage pools required to store backup data, Single Instance Storage (SIS) techniques are sometimes employed at each backup location. In SIS techniques, data is stored in segments, with each segment having a fingerprint that may be used to unambiguously identify it. For example, a data file may be segmented, and a fingerprint calculated for each segment. Duplicate copies of data segments are replaced by a single instance of the segment and a set of references to the segment, one for each copy. In order to retrieve a backup file, a set of fingerprints is sent to a backup server, where it is compared to the fingerprints of data stored in a storage pool. For each matching fingerprint, a data segment is retrieved. The resulting segments are re-assembled to produce the desired file.
In order to make data more readily available, one or more metadata managers may store metadata describing a single-instance storage pool in a database that is separate from the SIS pool itself. Such a database may be referred to as a metabase. Metadata managers may be located on separate hosts or co-located on hosts that include a database server. Accordingly, one or more metabases hosted in a variety of locations may contain data describing each SIS pool. Typically, metadata from a given backup agent is stored in only one metabase. As new backup agents are brought into a system, they may be assigned to either an existing metabase or a new metabase if the existing metabases are nearing their full capacity. Unfortunately, if a backup agent is assigned to a given metabase that is nearing full capacity, there may not be sufficient space available to store more metadata from the backup agent. One conventional approach to this problem is for a system administrator to redistribute backup agents among the available metabases. However, the expense and time involved in having a system administrator perform redistribution is undesirable. Further, additional time and effort is necessary to ensure that metadata from a given agent fits in a given metabase. These issues may also arise when new agents are added to a system.
In view of the above, an effective system and method for redistributing metadata among metabases that accounts for these issues is desired.